Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
In the normal ankle and foot there is an anatomical kinematic chain from the ankle joint to the toes. In particular, a normal foot has a series of articulations with increasing levels of motion, including the talocural (ankle) joint, the subtalar (heel) joint, the tarsal (midfoot) joint, and the metatarsals and phalanges (forefoot). The sequence of the articulations of a normal foot permit variations in lateral motions depending on the surface coming into contact with the foot, or the position of the body above the foot. When lower extremity amputations result due to abnormal development, trauma, diabetes, or some other medical condition, these amputations of the leg or ankle result in chronic disability. This is because conventional prosthetic foot designs do not sufficiently replace the anatomical function of the foot to accommodate sideways motions.